The invention relates to a device for the cyclic rearrangement of a pile of rectangular or square sheets, or a so-called "picture-changer".
Picture changers are known from U.S. Pat. Nos. 4,238,898, 4,238,899, 4,241,528, 4,241,529, 4,245,417, 4,259,802 and 4,376,348. These specifications are all based on the principle that a pile of pictures, especially photographic prints, is held by two frame parts that are movable relative to one another, one of which may have a viewing window. During each complete cycle of movement of the frame parts, that is, pulling them fully away from each other and sliding them fully back together again, one picture is removed from one end of the pile and returned to the other end of the pile again. The picture changers have the following components for this:
A feeding means feeds pictures to a separating means; the separating means detaches an individual picture from the pile; a retaining means holds the individual picture separated from the pile in one of the frame parts whilst the remainder of the pile is held in the other frame part; a guide means guides the separated individual picture such that it goes onto the other end of the remainder of the pile.
Although the known picture-changers are provided primarily for photographic prints, under certain circumstances they do not operate perfectly. That edge of a picture removed from the pile which faces the separating means should, when the frame parts are pushed together, be pushed from behind into a return gap. The separating means, in the form of a separator bar, presents an inclined face towards this edge, on which face the edge in question of the picture is to slide, while its opposite edge lies in front of a stop member of the other frame part. If, as is often the case, the photographs are badly bowed so that, for example, the edge facing the separator bar is approximately perpendicular to its inclined face, the picture may possibly be squashed up when the frame parts are pushed together instead of being conveyed back to the rest of the pile.
The aim of the invention is therefore to provide a picture-changer that operates reliably even with bowed sheets, especially photographs.